ASPIRIN

Adverse effects

Peptic ulcer disease and gastric irritation

Aspirin inhibits the production of prostacyclin (PGI2) and other prostaglandins. These normally cause vasodilatation in the capillaries supplying the GI mucosa and they inhibit excess acid secretion in the stomach. So, when someone takes aspirin and other NSAIDs, their gastric mucosa can break down, causing ulcers and bleeding.

Bleeding

As with all antiplatelet and anticoagulant drugs, aspirin can be associated with bleeding.

Aspirin is contraindicated in patients with active bleeding (e.g. peptic ulcer disease, intracranial haemorrhage) and should be used with caution in patients with risk factors that increase their risk of bleeding, such as:

≥75 years
History of bleeding
Recent trauma/surgery
Liver disease (clotting factors are made in the liver)
Concomitant use of NSAIDs or anticoagulants
Bleeding disorders

Patients may experience minor or major bleeding

GI bleed, intracranial haemorrhage, bruising, epistaxis

Bronchospasm

Aspirin inhibits the COX pathway leading to an up-regulation of the lipoxygenase pathway which produces leukotrienes.

Leukotrienes cause bronchospasm in the upper airways.

This is why leukotriene receptor antagonists (e.g. montelukast) are given in the management of asthma.

COX inhibition leads to the upregulation of lipoxygenase which synthesises leukotrienes.

Reye's syndrome

Reye's syndrome is a rare but serious illness (30% mortality) occuring mainly in children that take aspirin <2-3 weeks after a viral illness.

The combination of the effects of the virus and aspirin leads to damage of mitochondria in hepatocytes and subsequent liver failure. The liver is no longer able to metabolise ammonia compounds so ammonia builds up in the blood. It crosses the blood brain barrier where it causes inflammation and oedema resulting in life-threatening encephalopathy.

It is for this reason that aspirin is to be used with extreme caution in <16 year-olds.

In Reye's syndrome, liver failure leads to a build-up of ammonia in the blood and subsequent encephalopathy

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